Excerpts in this guide taken from:
Computer Shopper's Ultimate 2010 Power Supply Shopping Guide
written by: Denny Atkin
Computer Shopper's Ultimate 2010 Power Supply Shopping Guide
written by: Denny Atkin
You can find the full guide here, and we greatly encourage you to read through all of it! Ultimate Guide: How to buy a PC Power Supply
INTRODUCTION:
When it comes to building or upgrading a PC, the power supply is the least exciting piece of the puzzle. Oftentimes, it's just an afterthought. A bigger power supply doesn't make your PC run any faster, and it labors away day after day, hidden inside the case. Yet the power supply is actually one of the most important parts in any PC, considering that every component relies on it...Investing in a well-built power supply that can handle your computer's power needs—whether you’re replacing a failed supply or building a PC—can save you from migraine-grade headaches down the road.
WATTAGE, VOLTAGE & RAILS:
The next consideration is choosing a supply with enough wattage to power all the components in your computer. Looking at individual components can give you a general idea how much power you need. For example, if your video card (often the most demanding component in a high-performance PC) specifies that it requires a 400-watt power supply, but you also have a demanding CPU (such as an older high-end Phenom or Core 2 Quad chip) and multiple hard drives, you'll want to go with a higher wattage rating. But assessing your needs that way is an inexact science.
Another method: You can comb the support Web sites for the major components in your PCs; gather the individual power demands of the main parts, including your CPU, processor, and hard drives; and add those together to get a rough idea of how high a wattage your system requires.
You can also checkout Newegg.com's Power Supply Calculator to give you another estimate (DO NOT RELY ON THIS EXCLUSIVELY)
http://educations.newegg.com/tool/psucalc/index.html
With one of the calculators, getting a ballpark wattage number is easy. But in addition, you'll want to take a look at the number of “rails” in a given supply, and—more crucially—the amperage ratings of those rails. A “rail,” simply put, is an internal power path within a supply that provides a single voltage. A modern PC power supply will typically have a 3.3-volt rail, a 5-volt rail, and one or more 12-volt rails. The 12-volt rail is the critical one nowadays, as it's used by the most-demanding components of your PC: the processor and the graphics card. It basically boils down to a simple fact: Each device that plugs into a 12-volt connector requires a certain amount of amperage. A power supply with a single rail will have a single amperage rating, while a multi-rail power supply will break down the amperage available on each rail.
ON MULTIPLE RAILS, ETC:
Are multiple rails better than one high-amperage rail? Not necessarily. The ATX specification used to limit each individual 12-volt rail to 20 amps for safety purposes. However, when higher amperages turned out not to be a cause for concern, this limitation was dropped from the ATX spec. The number of rails mattered more when individual rails carried less power, as you could max out the available amperage on a single-rail system by connecting too many demanding components. Now that many single-rail power supplies have over 60 amps available on that one rail, that's much less of a concern.
The total amps available for 12-volt devices, whether they're all on one rail or split between multiple rails, is what really matters. You need to understand the rails concept, however, to make sense of the specifications that power-supply vendors use when expressing amperage. On the packaging or specification sheets for most power supplies, you'll find a chart that breaks down the amperage available on each rail.
EFFICIENCY:
The efficiency rating indicates how much energy a power supply delivers (in watts) divided by how much energy is fed into it. A 420W power supply with a 70% efficiency rating would consume 600W from the wall, giving off 180W of heat, and the 420W would be what the PC is actually able to use. (The higher the efficiency number, the less wastage.)
What should be immediately clear: All else being equal, a more efficient power supply not only wastes less energy, but it will run cooler and help keep system heat and fan noise down. As a result, in addition to the electricity and cost savings, higher efficiency ratings are desirable in power supplies intended for PCs with a crowded interior (such as small-form-factor or minitower models) or models used in a home-theater environment, where the drone of a fan would be a distraction.
The easiest way to find an efficient supply is to look for one with the 80 Plus logo on it. The 80 Plus program mandates that a computer power supply be 80 percent efficient or better at 20 percent, 50 percent, and 100 percent of rated load, with a power factor of 0.9. (“Power factor” is an advanced concept that’s part of the 80 Plus spec, but we’ll spare you the details—it’s well beyond the scope of this article.) The program was later expanded to include three additional ratings—80 Plus Bronze, 80 Plus Silver, and 80 Plus Gold—that indicate even greater efficiency.
HERE'S A CHART FOR ALL YOU GUYS!
It's always great to look for the 80+ seal on a PSU you are buying, but it's not the end of the world if it doesn't have it, especially when it comes to 80+ Silver and Gold ratings. Sometimes, the price just isn't worth the slight increase in efficiency.
Again, you can read all of this guide here: Ultimate Guide: How to buy a PC Power Supply
Any questions, feel free to post below!
INTRODUCTION:
When it comes to building or upgrading a PC, the power supply is the least exciting piece of the puzzle. Oftentimes, it's just an afterthought. A bigger power supply doesn't make your PC run any faster, and it labors away day after day, hidden inside the case. Yet the power supply is actually one of the most important parts in any PC, considering that every component relies on it...Investing in a well-built power supply that can handle your computer's power needs—whether you’re replacing a failed supply or building a PC—can save you from migraine-grade headaches down the road.
WATTAGE, VOLTAGE & RAILS:
The next consideration is choosing a supply with enough wattage to power all the components in your computer. Looking at individual components can give you a general idea how much power you need. For example, if your video card (often the most demanding component in a high-performance PC) specifies that it requires a 400-watt power supply, but you also have a demanding CPU (such as an older high-end Phenom or Core 2 Quad chip) and multiple hard drives, you'll want to go with a higher wattage rating. But assessing your needs that way is an inexact science.
Another method: You can comb the support Web sites for the major components in your PCs; gather the individual power demands of the main parts, including your CPU, processor, and hard drives; and add those together to get a rough idea of how high a wattage your system requires.
You can also checkout Newegg.com's Power Supply Calculator to give you another estimate (DO NOT RELY ON THIS EXCLUSIVELY)
http://educations.newegg.com/tool/psucalc/index.html
With one of the calculators, getting a ballpark wattage number is easy. But in addition, you'll want to take a look at the number of “rails” in a given supply, and—more crucially—the amperage ratings of those rails. A “rail,” simply put, is an internal power path within a supply that provides a single voltage. A modern PC power supply will typically have a 3.3-volt rail, a 5-volt rail, and one or more 12-volt rails. The 12-volt rail is the critical one nowadays, as it's used by the most-demanding components of your PC: the processor and the graphics card. It basically boils down to a simple fact: Each device that plugs into a 12-volt connector requires a certain amount of amperage. A power supply with a single rail will have a single amperage rating, while a multi-rail power supply will break down the amperage available on each rail.
ON MULTIPLE RAILS, ETC:
Are multiple rails better than one high-amperage rail? Not necessarily. The ATX specification used to limit each individual 12-volt rail to 20 amps for safety purposes. However, when higher amperages turned out not to be a cause for concern, this limitation was dropped from the ATX spec. The number of rails mattered more when individual rails carried less power, as you could max out the available amperage on a single-rail system by connecting too many demanding components. Now that many single-rail power supplies have over 60 amps available on that one rail, that's much less of a concern.
The total amps available for 12-volt devices, whether they're all on one rail or split between multiple rails, is what really matters. You need to understand the rails concept, however, to make sense of the specifications that power-supply vendors use when expressing amperage. On the packaging or specification sheets for most power supplies, you'll find a chart that breaks down the amperage available on each rail.
EFFICIENCY:
The efficiency rating indicates how much energy a power supply delivers (in watts) divided by how much energy is fed into it. A 420W power supply with a 70% efficiency rating would consume 600W from the wall, giving off 180W of heat, and the 420W would be what the PC is actually able to use. (The higher the efficiency number, the less wastage.)
What should be immediately clear: All else being equal, a more efficient power supply not only wastes less energy, but it will run cooler and help keep system heat and fan noise down. As a result, in addition to the electricity and cost savings, higher efficiency ratings are desirable in power supplies intended for PCs with a crowded interior (such as small-form-factor or minitower models) or models used in a home-theater environment, where the drone of a fan would be a distraction.
The easiest way to find an efficient supply is to look for one with the 80 Plus logo on it. The 80 Plus program mandates that a computer power supply be 80 percent efficient or better at 20 percent, 50 percent, and 100 percent of rated load, with a power factor of 0.9. (“Power factor” is an advanced concept that’s part of the 80 Plus spec, but we’ll spare you the details—it’s well beyond the scope of this article.) The program was later expanded to include three additional ratings—80 Plus Bronze, 80 Plus Silver, and 80 Plus Gold—that indicate even greater efficiency.
HERE'S A CHART FOR ALL YOU GUYS!
It's always great to look for the 80+ seal on a PSU you are buying, but it's not the end of the world if it doesn't have it, especially when it comes to 80+ Silver and Gold ratings. Sometimes, the price just isn't worth the slight increase in efficiency.
Again, you can read all of this guide here: Ultimate Guide: How to buy a PC Power Supply
Any questions, feel free to post below!
